According to some references found in the nano3G MIB help, the CellID as
reported in the HNB-REGISTER-REQ is combined from 16-bit CellID and the
12bit RNC-ID.
The HNB-GW should use this value in the register-req to ensure it is
unique in the network. We should probably reject register requests from
non-unique / overlapping values.
Change-Id: Ib58cc9f3c0e700f8bc5930f4df0d2dfe7888b991
Closes: OS#2789